The invention relates to a ground-drilling device comprising a main carriage displaceable on a mount.
In-case of ground-drilling devices, the rotatingly driven drill column is advanced toward the drill hole with a pressure force being generated during drilling. The drilling unit rotating the drill rod is arranged on a carriage displaceable along the track of a mount. Mostly, the mount is arranged on a vehicle and it can be pivoted about a horizontal axis in order to drill drill holes with different angles of inclination. Normally, the advancing force for the carriage is raised by a hydraulic motor driving a chain hoist which advances the carriage with a desired pressure force so that the drill rod is firmly pressed against the base of the drill hole. A chain drive, however, has the disadvantage that it requires a long stable chain having at least about twice the length of the mount. Such chain drives are susceptible to soiling and chain rupture. In particular, when concrete is to be introduced into the drill hole, there is the risk that the chain links are loaded with concrete. In addition, bulky reducing gears are typically required. Another disadvantage of the known chain drives for the advancement of the main carriage consists in that a chain drive operates jerky in the pitch of the chain links so that a sensitive smooth jerkless advancement is not possible. To withdraw the drill column out of the drill hole, a rapid drive is typically required which also requires the use of a bulky transmission (DE 29 24 393 C2).
The use of piston-cylinder units for the direct advancement of the main carriage on the mount has so far failed due to the fact that such a piston-cylinder unit has to project rearwardly far beyond the mount since the displacement track normally extends essentially over the entire length of the mount. Owing to a far-projecting piston-cylinder unit, the length of the ground-drilling device is substantially increased beyond the length of the mount.